International Hydrographie Review, Monaco, LXXII(l), March 1995 PROGRESS IN PRODUCING BATHYMETRIC CHARTS AT A GLOBAL AND REGIONAL LEVEL by Rear Admiral Christian ANDREASEN 1 Introduction This paper describes the progress of work to advance the production of bathymetric charts. This includes the IHO's present and historical role relating to the General Bathymetric Chart of the Oceans (GEBCO), and the work of the Intergovernmental Oceanographic Commission (IOC), in cooperation with the IHO and in developing regional bathymetric maps. Inspired originally by Prince Albert I of Monaco, the GEBCO world series of bathymetric charts is now in its Fifth Edition. This edition is now available in digital form on CD-ROM as the GEBCO Digital Atlas. This latest edition, printed and distributed in hard copy by the Canadian Hydrographic Service, has recently been digitized through an effort of the British Oceanographic Data Centre at Bidston, U.K. Considerations are now being given for updating of the digital data and the possibilities for a printed Sixth Edition. In recent years, the IHO designated the U.S.-NOAA's National Geophysical Data Center at Boulder, Colorado, as the IHO Data Centre for Digital Bathymetry. This Centre now provides a central depository for all ocean bathymetry greater than 100 meters in depth. The GEBCO series is published at a scale of 1:10 million to provide for total world coverage. The need for increasingly larger scales has most recently been addressed by the IOC's Regional Ocean Mapping Project at 1:1 million scale. Started in the Mediterranean, there are now several regional bathymetric mapping projects underway. Bathymetric maps at these small and medium scales provide a good basis for planning and support a wide variety of scientific activities in the oceans. One of the many problems being faced in these bathymetric mapping activities is the handling of the very dense data sets resulting from the deep ocean multibeam mapping systems. Another is to develop a rational system for naming the many new ocean features that are being discovered. 1 President, IHB Directing Committee, International Hydrographic Organization, Monaco. BACKGROUND Historically, as nations began to explore the world's oceans, nations held secret the information collected by their mariners for commercial and military advantage. About the turn of the century, as nations had become involved in world maritime trade, this attitude began to change. In 1899, during the Seventh International Geographic Congress in Berlin, Germany, a Commission was set up to study the naming of ocean relief features and to draw up plans for a general chart of the oceans. The Commission was composed of ten leading geographers and scientists of the day: H.SH. Prince Albert I of Monaco, Professor O. KRUMMEL, Admiral S.O. MAKAROW, Dr. H.R. M ILL, Sir John MURRAY, Dr. Fridtjof NANSEN, Professor O. PETERSSON, Baron RlCHTOFEN, Professor A. SUPAN and Professor J. T h o u l e t . The Commission next met in Wiesbaden, Germany, in 1903 under the Chairmanship of Prince Albert I. At this meeting, the Prince's offer to organize and finance the production of a new series to be designated "The General Bathymetric Chart of the Oceans (GEBCO)" was accepted. The series, at a scale of 1:10 million, was to be composed of 16 sheets on the Mercator projection, together with 8 sheets on gnomonic projection to cover the polar regions. Work began in 1903 on the First Edition and a team of seven draftsmen completed it in only 7 months. It included over 18,000 soundings and was presented to the Paris Academy of Sciences in 1904 and, later that year, to the Eighth International Geographical Congress at Washington, D.C. At the opening of the Oceanographic Museum at Monaco, in 1910, Prince Albert I called for experts to discuss the production of a Second Edition of GEBCO. The first sheets of the Second Edition were published in 1912, but because of the disruption of World War I, the Edition was not completed until 1930. This Edition was compiled from over 30,000 soundings. Through the time when this edition was compiled, available sounding data only consisted of point depths. Soundings in the deep ocean were taken at great effort, and only a few ships could actually take the time to stop and expend the time to lower a weighted wire to determine a single ocean depth. Because of this, only a few deep ocean soundings became available each year and updating of the data base could be done simply by publishing listings of the information collected by national Hydrographic Offices. Following the death of Prince Albert I, in 1922, and after the completion of the Second Edition, his team of scientists working on GEBCO was disbanded and the International Hydrographic Bureau (now the International Hydrographic Organization) was invited to take over the GEBCO project. In 1929, IHO took on the task of keeping the series up-to-date and collating the needed data. Data for a Third Edition were compiled by the IHB staff, and Hydrographic Offices of the IHO Member States were requested to supply available ocean soundings to the IHB. To collect and archive these data, the IHB established a series of 1001 plotting sheets (now 655 sheets) on the Mercator projection at a scale of 1:1 million. As a result of this global effort, when the International Council of Scientific Unions (ICSU) established the World Data Center network for the International Geophysical Year in 1957, the IHO was designated as the World Data Center for Bathymetry. From these 1:1 million scale plotting sheets, which formed a unique data base, the 1:10 million scale GEBCO series was derived. Although publication began in 1932, the outbreak of World War II disrupted the effort and the Third Edition was never completed. Due to the delay, significant new data had become available necessitating a renewed effort. The echo sounder had come into use prior to the war (about 1930) and the amount of available bathymetric data was increasing rapidly. The Vlth International Hydrographic Conference, in 1952, initiated work on a Fourth Edition. Two sheets were published in 1958-61 based on compilations by the IHB staff, but the amount of data becoming available is now beyond the capability of the small IHB staff. As a result, based on a decision of the 1962 International Hydrographic Conference, the maintenance of the 1:1 million plotting sheets covering the world's oceans was assumed by 18 "Volunteering Hydrographic Offices" (VHO's) of the IHO Member States. The allocation of the plotting sheets among the VHO's is given in IHO Publication B-2, "Catalogue of Bathymetric Plotting Sheets". By 1965, an agreement was made between the French Institut Géographique National (IGN) for the production of the GEBCO Fourth Edition. The IHO then coordinated the effort wherein Volunteering Hydrographic Offices provided updated sounding sheets which were used by IGN for compilation, with the French Hydrographic Office verifying the work. The overall project was overseen by the GEBCO Committee, which was drawn from IHO national Hydrographic Offices, the Scientific Committee on Oceanic Research (SCOR) and the International Association for the Physical Sciences of the Oceans (IAPSO). An Editorial Board of the Committee was responsible for the verification and correction of geomorphological details. Fifth Edition of GEBCO In 1972, the IHO and Intergovernmental Oceanographic Commission (IOC) of UNESCO entered an arrangement for co-sponsorship of a new edition of GEBCO. With the theory of plate tectonics having been developed and significant advances in marine science having been made, it was decided that a scientific approach should be taken for the compilation of a GEBCO Fifth Edition. This involved scientific analysis of data types other than bathymetry to provide inferences as to the major linear trends of seafloor features. This approach provided for a better compilation of bathymetric features than sparse bathymetric data alone could provide. This new approach took advantage of the strengths of the two organizations by employing experts for the IHO Hydrographic Offices and eminent marine geologists and geophysicists from IOC nominated after consultation with SCOR, IAPSO and the Commission for Marine Geology. The IHO retained its responsibility for maintaining the collected 1:1 million scale sounding sheets, a role of providing cartographic advice and supervision over the final GEBCO product. IOC provided the scientific input, essential for improved contouring of the bathymetric data and scientific peer review. Through close collaboration between members of the two organizations a product of improved quality resulted. As with any major project, financing became a major issue. The Chairman of GEBCO at the time was Mr. Gerald H. Ewing, Assistant Deputy, Minister of Fisheries and Oceans and former Dominion Hydrographer. Through his initiative, the Canadian Government agreed to fund the scribing and printing of the GEBCO Fifth Edition through the Canadian Hydrographic Service (CHS). Over the 1975-1982 time period, CHS completed the entire series of 18 Fifth Edition sheets. The Fifth Edition consists of 16 sheets on Mercator Projection at 1:10 million (at the Equator) and 2 sheets on Polar Stereographic Projection at 1:6 million scale (at 75 degrees latitude) (Fig. 1). Upon completion, CHS also produced a World Sheet giving global coverage at 1:35 million and 1:25 million (Polar regions) using the projections of the basic series. Bathymetry was depicted at 200 metres, 500 metres and at 500 metre intervals thereafter, with the contours displayed varying slightly because some sheets included intermediate contours to better delineate features. An important innovation with the Fifth Edition was the inclusion of information about the source data on each of the sheets.